U.S. patent number 4,659,197 [Application Number 06/652,511] was granted by the patent office on 1987-04-21 for eyeglass-frame-mounted eye-movement-monitoring apparatus.
Invention is credited to Lee S. Weinblatt.
United States Patent |
4,659,197 |
Weinblatt |
April 21, 1987 |
Eyeglass-frame-mounted eye-movement-monitoring apparatus
Abstract
A technique is disclosed for monitoring the eye movements of a
subject with apparatus that is removably attachable to the
subject's own eyeglass frame. The apparatus includes a light source
to bounce light off the subject's eye and a detector to sense the
reflected light. Both are adjustably mounted on a support. The
support includes several interlinked parts which are readily
adjustable to fit the subject's eyeglass frame.
Inventors: |
Weinblatt; Lee S. (Teaneck,
NJ) |
Family
ID: |
24617089 |
Appl.
No.: |
06/652,511 |
Filed: |
September 20, 1984 |
Current U.S.
Class: |
351/210; 351/158;
351/209 |
Current CPC
Class: |
A61B
3/113 (20130101) |
Current International
Class: |
A61B
3/113 (20060101); A61B 003/14 () |
Field of
Search: |
;351/209,210,158 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Methods and Designs, Survey of Eye Movement Recording Methods" by
Lawrence R. Young and David Sheena (Behavior Research Methods and
Instrumentation) 1975, vol. 7(5), pp. 397-429..
|
Primary Examiner: Bovernick; Rodney B.
Assistant Examiner: Dzierzynski; P. M.
Attorney, Agent or Firm: Langer; Thomas
Claims
I claim:
1. Apparatus adapted to be mounted on an eyeglass frame for
monitoring eye movements of a subject wearing said frame,
comprising:
a support including means for adjusting the dimensions of said
support to a plurality of differently configured eyeglass
frames;
fastening means for readily securing said support to said frame and
readily removing said support from said frame; and
detector means for sensing the eye movements of said subject and
including a light source means for reflecting light off the eye, a
light sensor for detecting the reflected light, and wire means for
activating the light source and for conveying signals detected by
said sensor, all of which being carried on said support.
2. The apparatus of claim 1, wherein said support comprises a
carrying surface and means accomodating said frame, said
accomodating means being removably securable to the frame by the
fastening means.
3. The apparatus of claim 1, wherein said support comprises a
generally U-shaped bar having a channel wider than said eyeglass
frame, said channel being bounded by two side walls and a top wall;
and said fastening means comprises at least one hole tapped into
one of said side walls, and a screw threaded into said at least one
wall which, when turned, secures the eyeglass frame betwen the tip
of said screw and the other of said side walls.
4. The apparatus of claim 2 wherein said adjusting means comprises
support bar means adjustably secured to said carrying surface of
said support, said sensor being attached to the support bar
means.
5. The apparatus of claim 4, wherein said support bar means enables
movement of said sensor means in at least two degrees of
freedom.
6. The apparatus of claim 5, wherein said support bar means
comprises a first support bar adjustably secured to said support
and a second support bar adjustably secured to said first support
bar, said sensor means being carried by the second support bar.
7. The apparatus of claim 6, wherein said support bar means
includes an extension means between the carrying surface and said
first support bar.
8. The apparatus of claim 7, wherein said light source is attached
to said support bar means.
9. The apparatus of claim 8, wherein said light source is carried
on a third support bar adjustably secured to the second support
bar.
10. The apparatus of claim 9, wherein said sensor is adjustably
connected to the second support bar and the light source is
adjustably connected to the third support bar.
11. The apparatus of claim 10 wherein the end of the third support
bar remote from its connection to the second support bar is
connected to a nose bridge grip securable to the nose bridge of the
eyeglass frame.
12. The apparatus of claim 11, wherein the nose bridge grip is
coupled to the third support bar and the first support bar is
coupled to the support, respectively, by vertically adjustable
means.
13. The apparatus of claim 12, wherein the first support bar is
rotatably secured toward one end to the support and toward its
other end to the second support bar, said second support bar being
rotatably secured near its ends, respectively to the first and
third support bars.
14. The apparatus of claim 13, wherein the first, second and third
support bars are adjustably secured to each other with pins of one
bar sliding, respectively, in a slot of another bar.
15. The apparatus of claim 14, further comprising means for
monitoring a scene being viewed by the subject, and second support
means removably secured to said eyeglass frame for carrying said
scene monitoring means.
16. The apparatus of claim 15, further comprising means for
superimposing the images detected by said scene monitoring means
and said detector means to provide a combined image of the scene
and the subject's eye movements.
17. The apparatus of claim 16, wherein said means for superimposing
is optical and comprises a housing to which is secured a first lens
means which is coupled to said detector means, and a second lens
means for picking up light from said first lens means, whereby the
second lens means transmits light to a video camera.
18. The apparatus of claim 17, wherein said detector means is
coupled to the first lens means by an optic fiber.
19. The apparatus of claim 18, further comprising means to adjust
the position of said first lens means relative to said housing.
20. The apparatus of claim 17, further comprising means to adjust
the position of said first lens means relative to said housing.
21. The apparatus of claim 20, further comprising a prism
interposed within said housing in the path of light between the
first lens means and said second lens means, and means to adjust
the position of said prism relative to said first lens means.
22. The apparatus of claim 17, further comprising a prism
interposed within said housing in the path of light between the
first lens means and said second lens means, and means to adjust
the position of said prism relative to said first lens means.
23. The apparatus of claim 22, further comprising a a third lens
means coupled to said scene monitoring means, said third lens means
being secured to said housing and aimed so that light from it is
picked up by the second lens means.
24. The apparatus of claim 21, further comprising a a third lens
means coupled to said scene monitoring means, said third lens means
being secured to said housing and aimed so that light from it is
picked up by the second lens means.
25. The system of claim 21, further comprising a semi-silvered
mirror secured in said housing with the first and third lens means
being aimed to direct light therefrom at said mirror, and said
second lens means being aimed to pick up the light from both first
and third lens means via said mirror.
26. The system of claim 25, wherein said prism is positioned
between the first lens means and said mirror.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a technique for monitoring the eye
movements of a subject wearing eyeglasses, and in particular to a
light, unobtrusive device easily and removably mountable on any
conventional eyeglass frame.
Equipment that can monitor the eye movements of a person in
response to certain visual stimuli is well known. Typically, the
subject would be exposed to a visual stimulus and his ocular
reactions recorded by a monitoring apparatus. Such an apparatus can
include a light source, visible or infrared, which is bounced off
the eye into a suitable detector. The detected signal is then
electronically processed to obtain a reading of the eye position at
any given time. Various such technologies are discussed in the
article "Methods and Designs, Survey of Eye Movement Recording
Methods" by Lawrence R. Young and David Sheena in the publication
Behavior Research Methods and Instrumentation 1975, Vol 7(5) pgs.
397-429.
Many applications exist for such an apparatus; these include
medical diagnosis, military uses such as weapons aiming, training
equipment such as aircraft simulators, sports analysis for
improving visual techniques and concentration, advertisement
testing, design planning as for an automobile dashboard, and
testing for visual impact as of highway and store signs. In some of
the listed applications, medical diagnosis and aircraft simulators
for example, the eye-movement-monitoring apparatus is stationary,
as is the equipment for presenting the visual stimuli, such as a
video monitor. Since the latter two are fixed, the viewer is also
stationary. Typically, the subject is seated and his head fixed in
place by a chin rest or a bit plate. However, in some applications,
the exposure to the requisite stimuli requires movement. Thus, if
analysis of a baseball batter's vision as he watches a pitched ball
is desired, it would be preferable to actually do that in a
batter's box in a realistic situation. Likewise, in advertising
applications a subject may be requested to walk down a supermarket
aisle so that his response to the most eye-catching containers can
be recorded. Stationary equipment obviously cannot accomplish such
tasks.
Head-mounted eye-movement-monitoring equipment has been devised
which obviates the need to keep the person's head fixed. Since the
equipment is affixed to the subject's head, it moves with his head
and provides an accurate signal regardless of how he moves it. Such
devices have been used in, for example, military applications where
head movement is essential (e.g. the helmet of a pilot) and even in
applications where head movement is not essential but preferable.
As regards the latter, a fixed position for the head is to be
avoided when the monitoring session is relatively lengthy because
the subject is likely to experience considerable discomfort after
awhile and a commensurate decrease in concentration. Various
head-mounted arrangements are available. For example, U.S. Pat. No.
4,102,564 issued July 25, 1978 to Henry L. Michael discloses a type
of arrangement including light sources and sensors mounted on a
helmet. U.S. Pat. No. 3,473,868 issued Oct. 21, 1969 to Young et
al. discloses a spectacle frame used in eye glasses. On the frame
are mounted a light source and detectors to sense the light
reflected by the eye to provide horizontal and vertical eye
movement measurements. However, no provision is made for specific
lens prescriptions in order to make it usable by many subjects.
Also, the frame is specially modified by supports secured
permanently to it to carry the monitoring devices.
My U.S. patent application Ser. No. 486,031 filed Apr. 18, 1983
discloses apparatus which is advantageously usable for eyeglass
wearers. An eyeglass frame is modified to include clips for
removably retaining corrective lenses. As described in that
application, the corrective prescription of the subject is
determined and appropriate lenses are selected from a stock kept on
hand at the testing site. The eyeglass frame is further modified by
an arrangement for adjustably carrying the light source and eye
movement detector on the frame. These are permanently affixed to
the frame.
Although the arrangement described in the above-mentioned patent
application is a substantial improvement over previously known
devices in that it provides a light, highly portable means which is
readily modifiable to the subjects's prescription, it nevertheless
has several disadvantages. For example, a stock of corrective
lenses must be kept on hand. Also, since only a reasonable number
of such lenses can be kept readily available, the subjects's
precise correction may not be available in which case only the
closest available prescription will be selected. However, this may
cause the subject some degree of distraction. Furthermore, since
the light source, eye movement detector and scene monitor are
affixed to a frame used for all subjects, a particular subject
cannot use his own frame. The standard frame he must use may cause
the subject some discomfort and may, thus, be the source of
additional distraction.
For specific applications, regardless of whether stationary or
head-mounted equipment is used, it is desirable to superimpose the
subject's eye movements on the viewed scene. This, of course,
requires not only eye movement monitoring equipment but also
apparatus for simultaneously detecting the scene being viewed.
Signals from the eye-movement-monitoring equipment and the scene
detection devices are electronically combined to attain the desired
superimposition. Thus, in the above-described sports situation, the
batter's eye movements would be superimposed on a scene showing
approach of the pitched ball toward him. Analysis is thus possible
of whether he is looking properly at the ball. In advertising, a
subject is shown a filmed advertisement. Both his response and the
ad are monitored. Combining the two enables the determination of
the portions of the advertisement to which the subject's eyes are
drawn and, thus, an analysis is possible of the effectiveness of
the advertisement in attracting the subject's attention, causing
him to look at the desirable portions, and creating a lasting
impression. See for example my U.S. Pat. No. 4,075,657 issued Feb.
21, 1978.
Equipment exists for accomplishing both aims of portability and
recordal of the viewed scene. See, for example, U.S. Pat. No.
3,542,457 issued Nov. 24, 1970 to Balding et al. It discloses two
helmet-mounted television cameras. One camera records an eye spot
generated by an optical system for monitoring eye movement. The
other camera is aimed at the scene being viewed. Signals from the
two cameras are mixed to obtain the requisite superimposition.
However, this and systems like it suffer from several
disadvantages. The bulk and weight of the equipment can cause
discomfort and fatigue. Also, the equipment blocks the vision of
one and eye and reduces peripheral vision in the other. This
interferes with depth perception and is a constant reminder of the
test situation and can, therefore, result in distorted responses.
Eyeglass wearers cannot use the equipment because the lenses can
distort the light from the optical monitoring equipment and since
the apparatus leaves too little clearance to accommodate glasses.
In addition, such equipment cannot readily be calibrated for the
eye shape of individual subjects.
The invention applies the corneal reflection method to monitor eye
movement. (See the above-mentioned Young and Sheena article). Eye
movement monitoring techniques using the corneal reflection method
must deal with another source of inaccuracy caused by the irregular
shape of the eye. In calibrating the testing apparatus used in
implementing such a technique, the subject is asked to look in the
center of the displayed scene which may be on a video monitor for
example, and the signal picked up from his eye with this monitoring
equipment is adjusted so that the resulting dot appears in the
center of the video monitor. Thus, the place where the subject is
looking and the dot generated by the monitoring equipment are made
to coincide. The subject is then asked to look at the upper right
hand corner of the displayed image, and the apparatus is
calibrated, as by operating a zoom lens, to place the signal
detected from the eye at the upper right hand corner of the video
monitor. In this manner, the monitored range of eye movement is
adjusted so it is equivalent to the size of the scene being viewed
by the subject. Were the subject's eye perfectly spherical, eye
motion to the lower left hand corner of the displayed scene would
accordingly place the resulting signal at the corresponding corner
of the monitor. However, due to the imperfect shape of the eye,
this usually does not occur. Thus, a correction must be provided so
that eye motion to any part of the screen is correctly and
accurately detected, recorded and interpreted despite the distinct
eye imperfections of individual subjects.
SUMMARY OF THE INVENTION
It is a general object of the invention to provide an improved eye
movement monitoring apparatus.
It is another object of the invention to provide an eye movement
monitoring apparatus which can be worn on an eyeglass frame.
A further object of the invention is to provide an eye movement
monitoring apparatus which can be removably secured to the eyeglass
frame of any individual.
Yet another object of the invention is to provide a light, compact,
relatively inexpensive and unobtrusive eye movement monitoring
apparatus that is removably securable to the eyeglass frame of any
individual.
Still another object of the invention is to provide an eye movement
monitoring apparatus that is removably securable to the eyeglass
frame of any individual in such a manner that it can be
conveniently and quickly secured to and removed from the eyeglass
frame.
Another object of the invention is to combine the monitored eye
movement signals with signals indicative of the scene being viewed
by the subject while his eye movements are being monitored.
One other object of the invention is to provide a correction for
imperfection in the eye shape of individuals which tend to distort
the monitored eye movements.
These and other objects of the invention are accomplished by one
aspect of the invention directed to apparatus adapted to be mounted
on an eyeglass frame for monitoring eye movements of a subject
wearing this frame. The apparatus comprises support, fastening
means for removably securing the support to this frame, and
detector means carried by the support for sensing the eye movements
of the subject.
Another aspect of the invention is directed to an
eye-movement-monitoring system for monitoring the eye movements of
a subject who is viewing a scene which comprises
eye-movement-detection means removably mounted on the eyeglass
frame normally worn by the subject, means for superimposing the
output from the eye-movement-detection means over the scene being
viewed by the subject, and transfer means for coupling the
eye-movement-detection means to the superimposing means.
These and other aspects of the invention will be explained below in
the detailed description of the drawings which is to be read and
interpreted in connection with the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of the preferred embodiment of the
invention;
FIG. 2 is a front view of the embodiment in FIG. 1;
FIG. 3 is a side view of the FIG. 1 embodiment;
FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 3;
and
FIG. 5 is a cross-sectional view of an optical system for combining
the eye movement and scene images.
DETAILED DESCRIPTION OF THE DRAWINGS
The preferred embodiment of the invention is comprised of the
following parts: a support 3 for removably mounting the eyeglass
mounted assembly 1 to an eyeglass frame, adjustment means 5 coupled
to support 3 for customizing the assembly 1 to the size and
configuration of the subject's particular frame, light source means
7 and detection means 9 mounted on the adjustment means in a manner
enabling further adjustment of each, respectively, and optical
means 11 for combining the scene and eye movement images in order
to superimpose the subject's eye movement on the scene being
viewed. Each of these parts is described in detail below.
As best shown in FIGS. 2 and 4, support 3 includes a generally
U-shaped bar with side walls 13 and 15 joined by top wall 17 to
form channel 19. Walls 13 and 17 are somewhat thicker than wall 15
because the former each must be tapped to accommodate a screw (as
described in detail below). The added thickness allows for tapping
an effective number of turns for the screw to be adequately held in
place. Although side wall 15 is relatively thin, it is rigid and
strong enough to withstand the pressure applied to it by turning of
the screw in wall 13.
Screw 21 is threaded into hole 23 tapped into wall 13 respectively
(See FIG. 4). Screw 21 is long enough to extend through side wall
13 and into channel 19 (see FIG. 3). Strip 24 is made of a durable
and resilient metal or metal alloy. It is bent to have its end
sections 26 and 28 joined by an angled center portion 30. When end
section 26 is secured to wall 13 of support 3, as with screws 32
and 34, the other end section 28 remains spaced from wall 15 by a
distance sufficient to receive the temple piece of an eyeglass
frame. As support 3 is placed over the temple piece 36 of eyeglass
frame 38, top wall 17 rests on temple piece 36 while side walls 13
and 15 are slightly spaced from it. Strip 24 may also be spaced
from it or just touching it. Screw 21 is tightened until the temple
piece is secured between strip 24 and side wall 15. Thus, the
length of screw 21 is such as to accommodate the thinnest glass
frames while channel 19 must be wide enough to accommodate the
thickest glass frames.
Adjustment means 5 is comprised of three bars linked together with
one being linked to support 3. More specifically, bar 27 is
generally rectangular and has a slot 29 and a tongue 31 as its
characteristic features. Slot 29 runs along much of the length of
bar 27 and snugly accommodates a slide 40 which, in turn has a slot
42 to receive the shaft of screw 33. Screw 33 is inserted into a
tapped hole (not shown) at one end of support 3 and has a head
bigger than the width of slot 42. When screw 33 is turned into
support 3, its head bears against slide 40 to secure it in place.
Screws 44 and 46 are usable to tighten bar 27 to slide 40. These
screws are received within tapped holes 28 (not shown) in bar 27
and, when turned, the screw tips bear firmly against slide 40 to
secure the two pieces to each other. Slide 40 adds additional
freedom of movement to adjustment means 5 in two ways. Firstly,
slot 42 contributes to the available distance bar 27 can be moved
relative to support 3. The distance is equal to the length of both
slots 29 and 42, rather than what otherwise would only be the
length of slot 29. Thus support 3 may be put a little further back
on temple piece 36 should that be convenient. Secondly, since
temple pieces and nose bridges have relative heights which vary
quite a bit on eyeglass frames of different types, slide 40 enables
bar 27 to be adjusted vertically relative to support 3 so the fit
on the nose bridge is precise (see below for more details). Screws
44 and 46 perform this tightening function also, of course. It
should be noted that only one of screws 44 and 46 is required to
bear against bar 27, not both. Which one is used depends on the
relative positions of bar 27 and slide 40. It should also be noted
that a plurality of tapped holes 28 (see FIG. 3) is provided along
the length of bar 27. Depending on what position is selected
between bar 27 and slide 40, one or both of screws 44 and 46 is
placed into the appropriate hole 28. The alternative of having a
screw in each of these holes is to be avoided in order to minimize
weight. This arrangement provides adjustability in both rotational
and longitudinal and directions. Thus, support 3 can be placed in
the most appropriate location on temple piece 36 of the subject's
frame and bar 27 is then moved backward, forward, or rotationally
to bring the rest of the assembly into proper position, as
described in more detail below.
Tongue 31 fits between prongs 35 of bar 37, as best seen in FIG. 3.
Holes, not shown, in tongue 31 and prongs 35 receive a screw 39
which also passes through washers 38 and 40. Washer 38 is tapped to
act like a nut. Bars 27 and 37, thus, rotatably coupled to each
other. They are tightened into position relative to each other with
screw 39. It is unnecessary to fully tignten screw 39. Since
assembly 1 is really secured in place to the eyeglass frame at its
ends (see below), screw 39 along with washers 38 and 40 are used to
establish sufficient friction between the prongs on the tongue to
keep the assembly from being loose and rotating too easily and
therefore uncontrollably.
The other end of bar 37 has another set of prongs, 41 and 42. It
also includes a slot 43 the reason for which will be discussed
below. Prongs 41 and 42 receive tongue 45 of bar 47 therebetwen, as
best seen in FIG. 3. Tongue 45 includes a slot 49. Screw 51 is
inserted through holes (not shown) in prongs 41, 42 and slot 49,
and it also passes through washers 50 and 52. Washer 52 is tapped
to act as a nut for screw 51. This arrangement permits bars 37 and
47 to slide and rotate relative to each other. They are fixed in
position relative to each other when screw 51 is sufficiently
tightened. Bar 47 further includes a slot 53 and a hole (not shown)
at the end remote from tongue 45. Received in such a hole is screw
54 within a sleeve 60 having a flared head 62 and an elongated
smooth shaft. Screw 54 is threaded into a a tapped hole (not shown)
in grip element 55. Grip element 55 has a U-shaped cross section so
it can straddle the nose bridge. Screw 56 is inserted into a tapped
hole (not shown) in bar 47 and can be tightened to bear against the
sleeve 60. Screw 56 and the elongated shaft of sleeve 60 enable
vertical adjustment of nose-bridge grip element 55 relative to the
rest of adjustment means 5. This, as said above with regard to
slide 40, allows adaptation of this arrangement to eyeglass frames
which vary as to relative position of the nose bridge and temple
piece.
Light source means 7 and detection means 9 are best shown in FIGS.
1 and 2. The two have supports which are identical in that they
provide adjustable retainers having a box 57 with an opening 59
therein and a carrier 61. Carrier 61 is U-shaped and has a tapped
hole (not shown) in the top and openings in the side walls. Upward
extending tongue 63 of box 57 also has a hole (not shown) and fits
between the side walls of carrier 61. Screw 65 is used to
rotationally couple and secure carrier 61 to box 57. Screw 67
provides rotational and longitudinal adjustment of light source
means 7 to bar 47 within slot 53 while screw 69 does likewise
within slot 43 of bar 37. Both screws 67 and 69 have knurled,
grippable head to facilitate making the necessary adjustments as
the equipment is worn by the subject.
Light source mean 7 utilizes a grain bulb and also an optical
arrangement (not shown) within tip 66. Wires 68 are connected to
supply power from a suitable source (not shown). The optical
arrangment is conventional in that it focuses the light from the
grain bulb to a point a preset distance from tip 66. Tip 66 has a
smooth barrel 70 so it can slide in and out of box 57 to enable the
operator to place the focused beam on the subject's eye. Set screw
90 in box 57 is then turned to secure barrel 70 in place.
Detection means 9 includes a terminator 72 to which fiber optic 74
is attached. An optical arrangement including conventional lenses
(not shown) is included in terminator 7 to pick up the light
reflected off the subject's eye. Set screw 76 is threaded into box
57 and is used to secure terminator 72 in place.
Although it is not a part of this invention, a scene monitoring
device 80 is shown in the drawings. It is disclosed in copending
application Ser. No. 572,818 filed Jan. 23, 1984. It is mounted on
temple piece 76 and is aimed at the scene being viewed by the
subject. It detects the viewed scene and conveys it by way of fiber
optic 88 to apparatus which combines the scene with the subject's
eye movements, as discussed in detail below.
Turning now to FIG. 5, an optical means 11 is shown for combining
the light received from the monitored eye movement and the scene
detector. Housing 77 has three openings therein. Opening 79
receives lens means 81 from the scene detectors, opening 83
accommodates lens means 85 from the eye movement monitoring means,
and opening 87 receives a coupling lens 89 to video cameras (not
shown). Mounted within housing 77 is a semi-silvered mirror
arrangement 91. This is a well known element for both transmitting
and reflecting light. Lens means 81, 85 and 89 are aligned with
mirror 91 so that light from means 81 is transmitted through mirror
91 into the video camera while light from means 85 is reflected by
mirror 91, also into the video camera. Thus, the video camera
"sees" light from both the eye movement monitor and the scene
monitor to achieve the desired superimposition.
Optical means 11 includes various adjustment and correctional
capabilities. Zoom lens 96 is usable to control the size of the
field of view as desired or appropriate. Depending on what is being
tested, be it a large billboard or a magazine page, the size of the
field of view will be adjusted accordingly. Lens means 85 from the
eye movement monitoring devices mounted on the eyeglass frame
includes a focusing lens 93, a zoom lens 95, and a movable support
97. Focus lens 93 is provided to add a degree of adjustability to
control the light detected off the eye as it is transmitted to the
video camera. This has the effect of improving resolution. Zoom
lens 95 is used in calibrating the range of eye motion of each
individual subject to correspond to the scene size provided by
scene monitor 80 and adjusted by zoom lens 96. Support 97 is
coupled to lead screw 99 to enable movement of support 97. As screw
99 is turned, it moves support 97 with respect to housing 77. This
is done for reasons discussed below. Another such screw (not shown)
is included to move support 97 along a perpendicular axis. Finally,
prism 101 is coupled to screw lead 103. As screw 103 is turned, it
moves prism 101 relative to housing 77 and support 97 for reasons
discussed in detail below.
In operation, the equipment is mounted and calibrated as follows.
The eyegalss frame is removed from the subject's head. Support 3 is
placed on the temple piece near the hinge if possible, and screw 21
is turned to press strip 24 against the temple piece. The various
elements of adjustment means 5 are then manipulated so that grip
element 55 can be placed on the nose bridge of the eyeglass frame.
This involves rotation and sliding of the various links as well as
height adjustment using slide 40 and sleeve 60 to compensate for
the height differential that exists, if any, between the nose
bridge and temple piece. The object is to have light source means 7
and detection means 9 at approximately the same height. FIG. 2
shows them horizontal to each other, and this is how it should
be.
The eyeglass frame is then placed on the subject's head and the
light source is then activated. The equipment operator slides the
barrel 70 of the light source relative to box 57 until he sees the
emitted dot of light focused on the camera. This may require
movement and rotation of box 57 relative to bar 47 until the dot is
properly placed. Once this is done, screw 67 is tightened to secure
the light source means 7 relative to bar 47 and set screw 70 is
tightened to secure the barrel 70 in place relative to box 57.
Scene detector means 80 is then placed on the eyeglass frame or, of
course, it could have been placed together with the eye movement
monitoring apparatus. Optic fiber 88 from the scene monitor means
87 and optic fiber 74 from the eye movement monitoring apparatus
are coupled to optic means 11 as described above. The lens of scene
monitor 80 is aimed at the scene and zoom lens 96 is adjusted so
the desired portion of the scene substantially fills the video
monitor (not shown). The subject is then asked to look at the
center of the displayed scene. Detection means 9 is then adjusted
by rotating and sliding box 57 until the dot generated by light
reflected by the subject's cornea is approximately also in the
center of the video monitor. Screw 69 is then tightened. Further
adjustment of the dot due to reflected light off the eye is done by
slightly moving support 97. Of course, more precise adjustment is
possible with the eyeglass frame mounted apparatus without resort
to optic means 11. However, such adjustment once the eyeglasses are
worn may cause the subject some discomfort. Therefore, the
adjustment is preferably made with optic means 11.
The mentioned adjustment is accomplished by turning screw 99. This
can be called an X-axis adjustment. A similar adjustment is made
with another screw (not shown) to provide a Y-axis adjustment.
Once the eye position dot is at the center of the video monitor,
the subject is asked to look at the upper right corner of the
scene. If the dot does not appear there, zoom lens 95 is adjusted
accordingly. This should also serve to correspondingly correct for
eye travel to the lower left hand corner. However, it has been
found that due to irregularities in eye shape, this may not occur
as explained above.
A correction is provided for such an irregularity where eye shape
results in a different incremental detected eye movement depending
on whether the eye moves to the right or to the left. This is
behind the use of prism 101. Prism 101 bends the light passing
between support 97 and mirror 91. The extent to which the light is
bent depends on where on the prism it hits. Thus, the light rays
are bent less near tip 105 and more near base 107. The equipment
operator determines the difference between the detected eye
movement in the right and left directions by viewing a monitor on
which the scene and eye movement outputs are superimposed, and then
turns screw 103 until the difference is eliminated or at least
minimized.
It will be apparent that several modifications can readily be made
to the above-described preferred embodiment of the invention. For
example, one of zoom lenses 95 and 96 can be dispensed with. Also,
the focus and zoom lenses can be mounted on the eyeglass frame if
the added weight is not considered a problem. All such
modifications are intended to be included within the scope of this
invention as defined by the following claims.
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